Treatment using fixed film processes and ballasted settling

ABSTRACT

A system and method is provided for water and wastewater treatment. The system comprises a fixed film biological process and a ballasted flocculation process.

FIELD OF TECHNOLOGY

One or more aspects of the disclosure relate generally to water andwastewater treatment, and more particularly to systems and methods forwater and wastewater treatment using fixed film processes and ballastedsettling.

SUMMARY

A system for treating wastewater is provided. The system comprises afixed film reactor fluidly connected to a source of wastewater andconfigured to provide a fixed film effluent. The system furthercomprises a source of ballast fluidly connected to the fixed filmeffluent and configured to provide a ballasted effluent. A clarifier isprovided in the system that is fluidly connected to the ballastedeffluent. The clarifier comprises a treated effluent outlet and aballasted solids outlet and is configured to separate a treated effluentfrom a ballasted solids.

A method for treating a wastewater is also provided. The methodcomprises introducing a source of wastewater to a fixed film reactor toprovide a fixed film effluent. The method further comprises adding aballast to provide a ballasted effluent. The method further comprisesseparating the ballasted effluent into a treated effluent and aballasted solids in a clarifier, and separating the ballasted solidsinto a recovered ballast and a ballast-free solids. The method furthercomprises adding the recovered ballast to the coagulated effluent.

A method for retrofitting a wastewater treatment system is alsoprovided. The wastewater treatment comprises a fixed film bioreactor anda clarifier positioned downstream of the fixed film bioreactor. Theclarifier comprises a solids outlet. The method for retrofittingcomprises installing a coagulation tank in the clarifier, and installinga ballast feed tank connected downstream of the coagulant tank in theclarifier. The method of retrofitting further comprises connecting thesolids outlet of the clarifier to the ballast feed tank.

DESCRIPTION OF THE DRAWINGS

The accompanying drawings are not intended to be drawn to scale. Forpurposes of clarity, not every component may be labeled in the drawings,nor is every component of each embodiment of the disclosure shown whereillustration is not necessary to allow those of ordinary skill in theart to understand the disclosure.

In the drawings:

FIG. 1 presents a schematic of a treatment system implementing a fixedfilm process, ballasted settling, and recovery of ballast in accordancewith one or more embodiments of the disclosure; and

FIG. 2 presents a schematic of reaction tanks integrated into aclarifier tank in accordance with one or more embodiments of thedisclosure.

DETAILED DESCRIPTION

Systems and methods are provided for treating water or wastewater. Thesystems and methods may comprise treating a water or wastewater in afixed film reactor, also referred to as a fixed film biological systemor attached growth system. The systems and methods may further comprisetreating the effluent from the fixed film biological system in aballasted settling process, or a ballasted flocculation system.

A fixed film biological system may oxidize and reduce soluble substrate,eliminating impurities and producing solids. Fixed film processes maymaintain biological growth on a surface or inert carrier or sheet andthe treated effluent from the fixed film bioreactor may contain about 50milligrams per liter (mg/l) to about 300 mg/l of biological solids. Incertain embodiments, the treated effluent may contain between about 100mg/l to about 200 mg/l. In certain embodiments, the treated effluentfrom the fixed film bioreactor may contain about 50 mg/l to about 2,000mg/l of biological solids Examples of fixed film processes include,without limitation, moving bed bioreactors (MBBR's), trickling filters,and rotating biological contactors. Typically, wastewater is filteredthrough a primary or coarse screen and/or is treated in a primaryclarification unit. Effluent of these primary processes or a rawwastewater may enter a fixed film biological system where solublesubstrate is oxidized or reduced to biological solids in the form ofslough from the fixed biomass on the inert carrier or sheet of the fixedfilm reactor. Aeration may be supplied in aerobic zones to supply oxygenand mixing to the system. In anaerobic, anoxic, or aerated anoxic basedsystems, mixers or mixers with aeration may be provided to maintainmixing throughout.

The fixed film biological system may provide an effluent comprisingbiological solids, often referred to as slough, which requiresseparation from a treated effluent in a downstream process. While fixedfilm processes have a small footprint, effluent biological solids fromthe process are often difficult to settle with conventionalsedimentation processes frequently requiring a large settling area.Clarification, therefore, is often the limiting step in the rate ofwastewater treatment involving fixed film biological systems or fixedfilm reactors.

Ballasted flocculation systems or ballasted settling systems maycomprise the addition of a coagulant, ballast, and, optionally, aflocculant to improve the removal of dissolved, colloidal, particulateand microbiological solids. In certain embodiments, the coagulant may beoptional. For example, ballast and flocculant may be added, withoutcoagulant. In other embodiments, ballast may be added without coagulantand flocculant. In other embodiments, ballast and coagulant may beadded, without flocculant. The precipitation and enhanced settlabilityof ballasted solids provides for a small clarification step, which mayallow for a small footprint system comprising biological andclarification steps. According to embodiments of the present disclosure,ballasted flocculation systems may eliminate the need to provide asecondary clarifier directly downstream of a fixed film biologicalsystem or reactor. Further, the ballasted flocculation system may beinstalled between the fixed film bioreactor and the secondary clarifier,thereby using the existing secondary clarifier as the ballastedflocculation clarifier and eliminating the need for a new clarifier.

Flocculation may be a process of contact and adhesion whereby particlesand colloids in liquid such as a water or wastewater form larger-sizeclusters of material. Particles may cluster together into a floc. Aflocculant may comprise a material or a chemical that promotesflocculation by causing colloids and particles or other suspendedparticles in liquids to aggregate, forming a floc. Polymer may be usedas flocculants. For example, acrylic acid/acrylamide copolymers andmodified polyacrylamides may be used.

Coagulation may be a process of consolidating particles, such ascolloidal solids. Coagulants may include cations, such as multivalentcations. They may include cations such as aluminum, iron, calcium ormagnesium (positively charged molecules) that may interact withnegatively charged particles and molecules that reduce the barriers toaggregation. Examples of coagulants include bentonite clay, polyaluminumchloride, polyaluminum hydroxychloride, aluminum chloride, aluminumchlorohydrate, aluminum sulfate, ferric chloride, ferric sulfate, andferrous sulfate monohydrate.

According to some embodiments of the disclosure, a fixed film biologicalsystem may be used in conjunction with ballasted clarifiers to treatwater or wastewater. The systems and methods of the present disclosuremay be particularly advantageous, for example, in treatment plants wherea small footprint is required such as, for example, a retrofit forindustrial plants, small flow plants or package plants, hybridwastewater plants, combining fixed film processes and activated sludgeprocesses, and lagoon plants requiring nitrification. Also, thiscombination may be used in small flow systems that do not havesignificant operator interface yet require a high quality effluent. Theuse of a fixed film process in combination with ballasted settling isnot limited to the examples given. Many uses in biological and chemicaltreatment of wastewater or potable water are possible.

In certain embodiments, a fixed film process followed by a ballastedflocculation process may be utilized for biological treatment of wateror wastewater to remove at least one of nitrogen compounds, such asnitrates, biological oxygen demand (BOD), chemical oxygen demand (COD),and phosphorus compounds. Fixed film processes may oxidize ammonia tonitrate and/or reduce nitrate to nitrogen gas. Biological solidsproduced may then be removed in addition to dissolved, colloidal andparticulate solids by the ballasted clarifiers. In certain embodiments,at least one of nitrogen compounds, such as nitrates, biological oxygendemand (BOD), chemical oxygen demand (COD), and phosphorus compounds maybe removed prior to disinfection to provide potable water or drinkingwater to distribute it to a water supply grid.

Ballasted flocculation systems may comprise the addition of a coagulant,a ballast and, optionally, a flocculant to improve the removal ofdissolved, colloidal, particulate and microbiological solids. In certainembodiments, the coagulant may be optional. For example, ballast andflocculant may be added, without coagulant. In other embodiments,ballast may be added without coagulant and flocculant. In someembodiments, ballast and coagulant may be added, without flocculant. Incertain embodiments, a magnetic ballast may be used.

The enhanced settlability of these ballasted solids may provide for asmall clarification step, which may allow for a small footprint systemcomprising biological and clarification steps. Recirculation of solids,either ballasted solids or ballast-free solids, to at least one of theballasted flocculation processes, such as the ballast mixing step, andto the fixed film process can further enhance the reliability of theoverall system. These features may be utilized in existing wastewatertreatment plants, small flow plants or package plants, combined seweroverflow (CSO) treatment plants, new plants that require a smallfootprint, hybrid treatment plants (fixed film and activated sludge),and lagoon treatment plants requiring nitrification. One benefit is thatan existing clarifier downstream of a fixed film process is readilyconvertible to a ballasted system using the system of the presentdisclosure. Conventional clarifiers may be even more readily convertibleif the ballasted system uses a magnetic material, for example,magnetite, as the ballast.

In some embodiments of the disclosure, a system for treating wastewateris provided. The system comprises a fixed film reactor fluidly connectedto a source of wastewater and configured to provide a fixed filmeffluent. A fixed film biological system may be employed which maycomprise one or more fixed film reactors, which are utilized in parallelor in series, and in which one or more of the fixed film reactors isoperational at a given point in time. In certain embodiments, the fixedfilm effluent may comprise about 50 mg/l to about 300 mg/l of biologicalsolids. The fixed film effluent may flow to a ballasted flocculationsystem in which a source of coagulant may be fluidly connected to thefixed film effluent and configured to provide a coagulated effluent. Thesource of coagulant may be optional. A source of ballast may be fluidlyconnected to the coagulated effluent and configured to provide aballasted effluent. In some embodiments, the source of ballast may befluidly connected to at least one of the fixed film effluent or thecoagulated effluent. The source of ballast may comprise a powderedballast. The ballast may not be in a liquid such that it may be added indry powdered form. In some embodiments, the ballast may be added by anoperator or by machinery, such as by a dry feeder. It is to beunderstood that the source of ballast being fluidly connected to thefixed film effluent or the coagulated effluent, or to any effluent orwastewater stream of the system, may comprise the source of ballast maybe in a dry (non-liquid) or powdered form. A clarifier may be fluidlyconnected to the ballasted effluent, the clarifier comprising a treatedeffluent outlet and a ballasted solids outlet and configured to separatea treated effluent from a ballasted solids. The ballasted solids outletof the clarifier may be fluidly connected to at least one of thecoagulated effluent and the fixed film reactor. In some embodiments, theballasted solids outlet may be fluidly connected to the source ofballast.

Optionally, a source of flocculant may be fluidly connected to theballasted effluent. At least one of the sources of coagulant, ballastand flocculant may be provided in line to a fixed film effluent stream.Alternately, tanks may be used such that the fixed film effluent flowsto a coagulant tank, into which a coagulant is added from a source ofcoagulant. The coagulated effluent may then flow to a ballast tank, intowhich a ballast is added from a source of ballast. The ballastedeffluent may then flow to a flocculant tank, into which a flocculant isadded from a source of flocculant. The flocculant effluent may then flowto the clarifier. In certain embodiments, a flocculant tank and sourceof flocculant may not be included in the ballasted flocculation system,and the ballasted effluent may flow directly to the clarifier. In someembodiments, a coagulant tank and source of coagulant may not beincluded in the ballasted flocculation system.

As discussed above, the ballast may be a magnetic ballast. The magneticballast may comprise an inert material. The magnetic ballast maycomprise a ferromagnetic material. The magnetic ballast may compriseiron-containing material. In certain embodiments, the magnetic ballastmay comprise an iron oxide material. For example, the magnetic ballastmay comprise magnetite (Fe₃O₄). The magnetic ballast may have a particlesize that allows it to bind with biological flocs to provide enhancedsettling or clarification, and allow it to be attracted to a magnet sothat it may be separated from the biological flocs. The particle size ofthe magnetic ballast may be less than about 100 micrometers (μm). Theparticle size of the magnetic ballast may be less than about 40 μm. Theparticle size of the magnetic ballast may be less than about 20 μm.

Sand ballasted systems often implement larger ballast size toeffectively recover the ballast. Ballast is also non-magnetic. Sandballasted systems have also implemented the use of cleaning agents toseparate the biological solids from the sand particles. This could be aresult of a large surface for bacteria to attach, requiring more thanshearing forces of a vortex mechanism alone to remove biological solidsfrom the sand particle surface, or the need to dissolve chemical bondsthat assist in the binding of the ballast.

Unlike sand based ballast that requires growth of floc around relativelylarge size sand particles, magnetite ballast can be used with smallsize, such as less than about 100 μm, allowing for the magnetiteparticles to impregnate existing floc. The result may be an enhancedseparation of flocculants. The ballasted effluent or the flocculanteffluent may be directed to at least one clarifier where ballastedsolids, such as magnetite ballasted solids, may be removed by gravity atan enhanced rate greater than conventional gravity clarifiers. Theclarifier, being configured to provide a treated effluent and aballasted solids, may be fluidly connected to at least one of the sourceof ballast, the coagulated effluent, and the fixed film reactor. Incertain embodiments, the ballasted solids outlet of the clarifier may befluidly connected to at least one of the coagulated effluent and thefixed film reactor. This may allow at least a portion of the ballastedsolids to return to the fixed film biological system and to the sourceof ballast, for example, the ballast tank connected to a source ofballast. A portion of the biological solids may also be removed from thesystem. This may involve utilizing a magnetic separation apparatus,which may allow recovery of magnetic particles, which would not befeasible with, for example, sand particles. In certain embodiments,mechanical shearing may be employed to shear the biological solids priorto ballast recovery, for example, prior to magnetite recovery. In someinstances, such as re-seeding and high flow events, a portion of thesettled biological solids may be recycled to the front of the fixed filmsystem. These solids may either be ballasted or solids stripped ofmagnetite through the magnetic separation. In certain embodiments, suchas small-scale operations, it may not be necessary or feasible torecover the ballast, such as the magnetic ballast from the system.

In certain embodiments, the system may be configured to treat betweenabout 200 gallons per day per square foot of a surface area of theclarifier to about 2,000 gallons per day per square foot of the surfacearea of the clarifier. In certain embodiments, the system may beconfigured to treat between about 200 gallons per day per square foot ofa surface area of the clarifier to about 6,000 gallons per day persquare foot of the surface area of the clarifier. In certain otherembodiments, the system may be configured to treat between about 100gallons per day per square foot of a surface area of the clarifier toabout 36,000 gallons per day per square foot of a surface area of theclarifier.

In certain embodiments, a ballasted recovery system may be positioneddownstream of the ballasted solids outlet of the clarifier. Theballasted recovery system may be positioned upstream of at least one ofthe source of ballast and the fixed film reactor.

In certain embodiments, the use of a magnetic ballast providesadvantages over use of other ballast materials. For example, the use ofa magnetic ballast provides for enhanced removal of biological solidsfrom the ballast. For example, a magnetic drum may be used to separatethe biological solids from the magnetic ballast. Optionally, mechanicalshearing may be utilized prior to separation. This process maysufficiently remove the biological solids from the ballast.Recirculation of settled solids to the reaction tanks further enhancesperformance and reliability while the optional recycle to the fixed filmsystem, whether with ballasted or ballast-free solids, allows foradditional flexibility for treatability and recovery in process upsetsor startups. In certain embodiments, cleaning solutions may beunnecessary in separating ballast from the biological solids.

A system for treating wastewater is shown in FIG. 1. A source ofwastewater, stream 1, which may be screened wastewater or primaryclarification effluent, enters fixed film biological system or fixedfilm reactor 4. Fixed film reactor 4 may comprise a moving bedbioreactor, a trickling filter, or a rotating biological contactor, forexample. Soluble substrate may be oxidized or reduced to biologicalsolids in the form of, for example, a slough, from the fixed biomass onan inert carrier or sheet of fixed film reactor 4. Aeration may besupplied in aerobic zones to supply oxygen and mixing for the reactor 4.In the case of anaerobic or anoxic based systems, mixers can be providedto keep the system fully mixed. Fixed film effluent 5 exits the reactor4. Fixed film effluent 5 comprises wastewater and solids produced inreactor 4. Fixed film effluent 5 enters a series of feed reaction areaswhich may be inline or utilize tanks.

Source of coagulant 7, such as metal or prehydrolized metal salt, isadded in reaction area 6 to provide a coagulated effluent. Followingcoagulation addition 6, flow continues on to ballast reaction area 8.Source of ballast, is introduced to provide a ballasted effluent. Thesource of ballast may comprise raw ballast 9, recycled or recoveredballast 10, recycled ballasted solids 11, or combinations thereof. Theballast may comprise a magnetic material. The ballast may comprise aferrous material. The ballast may comprise magnetite (Fe₃O₄). Theballast may be in powdered form. Raw ballast 9, or fresh ballast, isballast that has not before been introduced to the waste system.Recycled or recovered ballast 10 is ballast that is separated fromsolids in another part of the system, for example, recovery system 20,described below, and recycled to the ballast reaction area. Ballastedsolids comprise biological solids impregnated or partially impregnatedwith ballast. Recycled ballasted solids 11 are ballasted solids returnedto the ballast reaction area 8 from an outlet of the clarifier 15without first being introduced to a recovery system 20 for separation.

After ballast addition 8, source of flocculant 13 may optionally beadded in flocculant reaction area 12 to further flocculate solids andballasted solids prior to being introduced into clarifier 15. Flocculant13 may comprise a polymer.

As discussed below, clarifier 15 incorporated into the wastewatertreatment system may be a converter or retrofitted clarifier. Thedetails and particular components of the clarifier may be chosen by aperson of ordinary skill in the art as required. The clarifier may, forexample, comprise lamella. The clarifier may be configured to separatetreated effluent 16 from ballasted solids 24 and comprises outlet 26 fortreated effluent 16 and outlet 28 for ballasted solids. Solids settle inclarifier 15 and separated treated effluent 16 continues on to furtherdisinfection if required. A portion of the settled solids may berecycled ballasted solids 11 returned to ballast reaction area 8. Inaddition or in the alternative, another portion of the ballasted solids23 may be recycled to fixed film system 4.

At least a portion of settled solids 17 may be introduced into a ballastrecovery system 20. Optionally, settled solids 17 may first beintroduced to mechanical shearing device 19 to aid in breaking up theballast and non-ballast components of the settled solids. Alternatively,the mechanical shearing device 19 may be by-passed by stream 18. Theballast recovery system 20 may comprise a magnetic separator. Forexample, the separator may be a wet drum magnetic separator. In a wetdrum magnetic separator, magnetic ballast adheres to the surface of arotatable drum and is directed to a separate outlet from nonmagneticcomponents, or ballast-free solids, of the feed. Stripped solids maycomprise waste sludge 21 that exits the system 20 for further solidwaste treatment and disposal. A portion of these stripped solids, orballast-free solids, may optionally be recycled to fixed film system 4via optional feed line 22. It should be understood that ballast-freesolids refers to solids that have a majority portion of the ballastremoved from the solids. In some embodiments, at least about 90% of theballast has been removed. In other embodiments, at least about 95% ofthe ballast has been removed.

Additional optional components include clarifier 3 fluidly upstream offixed film system 4, and bypass line 2 which may allow stream 1 tobypass fixed film system 4 if necessary, for example, during a high flowevent, such as a rainfall or storm event.

In certain embodiments of the present disclosure, a method of treating awastewater may be provided. The wastewater may be treated at a ofbetween about 200 gallons per day per square foot of a surface area ofthe clarifier to about 2,000 gallons per day per square foot of thesurface area of the clarifier. In certain embodiments, the system may beconfigured to treat between about 200 gallons per day per square foot ofa surface area of the clarifier to about 6,000 gallons per day persquare foot of the surface area of the clarifier. In certain otherembodiments, the system may be configured to treat between about 100gallons per day per square foot of a surface area of the clarifier toabout 36,000 gallons per day per square foot of a surface area of theclarifier. In certain embodiments, the rate may be an average rate overa predetermined period of time. The method may comprise introducing asource of wastewater to a fixed film reactor to provide a fixed filmeffluent. The fixed film effluent may comprise about 50 mg/l to about300 mg/l of biological solids. In other examples, the fixed film maycomprise about 50 mg/l to about 2,000 mg/l. The method may furthercomprise optionally adding a coagulant to provide a coagulated effluent.In some embodiments, the coagulant may be added to the fixed filmeffluent. The method may further comprise adding a ballast to provide aballasted effluent. In some embodiments, the ballast may be added to atleast one of the fixed film effluent and the coagulated effluent. Theballast may comprise a magnetic material. The ballast may comprisemagnetite. The method may further comprise separating the ballastedeffluent into a treated effluent and a ballasted solids in a clarifier.The ballasted solids may include a small amount of residual ballast-freesolids and other residual components, as separation processes andballasting processes will never be perfectly complete. The method mayfurther comprise separating the ballasted solids into a recoveredballast and a ballast-free solids. Once again, the recovered ballast mayalso comprise some residual non-ballast components. Likewise, theballast-free solids may comprise some residual ballast. The method mayfurther comprise adding the recovered ballast to the coagulatedeffluent.

The method may also further comprise adding a flocculant to theballasted effluent. The method may also further comprise adding aportion of the ballast-free solids to at least one of the source ofwastewater, the fixed film effluent, and the coagulated effluent. Themethod may also further comprise adding a portion of the ballastedsolids to at least one of the source of wastewater, the fixed filmeffluent, and the coagulated effluent. The method may also furthercomprise adding a portion of the ballast-free solids to at least one ofthe source of wastewater and the coagulated effluent. The method mayalso further comprise adding a portion of the ballasted solids to atleast one of the source of wastewater and the coagulated effluent.

Wastewater treatment systems and methods such as those disclosed abovemay be accomplished by constructing reaction tanks directly inside aclarifier. This clarified unit may be constructed as part of a newwastewater treatment system or may be constructed as part of aretrofitting. Such a configuration may address potential obstacles tothe disclosed wastewater systems and methods including locating thereaction tanks, and minimizing the length of pipe run between thereaction tanks and clarifier. The tanks could be constructed of mildsteel, concrete, stainless steel, fiberglass, or the like. Constructionof reaction tanks directly inside a clarifier would minimize thefootprint and capital cost associated with installation of the disclosedsystem, particularly in cases where existing clarifiers would requiremodifications to make them work better in a ballasted flocculationsystem. These existing clarifiers are often oversized for the task ofsettling ballasted floc, and therefore the extra space may be used toincorporate reaction tanks by installing the reaction tanks inside theclarifiers. This effectively reduces the hydraulic retention time of theover-sized clarifiers, minimizes the required footprint of the watertreatment system installation, and provides the opportunity to usecommon wall construction to further reduce capital cost. Clarifiersdesigned for ballasted clarification do not typically include scumcollection systems, so there would be no interference of the reactiontanks with such a system.

A schematic of an embodiment of a system is shown in FIG. 2. System 200comprises clarifier 205. Integrated into clarifier 205 may becoagulation tank 210, ballast feed tank 215, and flocculation tank 220.Source of coagulant 235 may be fluidly connected to coagulation tank210. Source of ballast 240 may be fluidly connected to ballast feed tank215. The ballast may comprise a magnetic material. For example, theballast may comprise magnetite. The magnetite may be in powdered form.Source of ballast 240 may be introduced to ballast feed tank 215. Forexample, the delivery may be accomplished automatically through acontrol system or manually. The delivery of ballast may be continuous orit may be intermittent. Likewise, for coagulant and flocculant deliverymay be automatic or manual, and continuous or intermittent. Optionally,source of flocculant 245 may be fluidly connected to an optionalflocculation tank 220. The flocculant may comprise, for example, apolymer. While the present embodiment has all three tanks incorporatedinto the clarifier, other combinations are possible. For example,coagulant tank 210 may be located outside clarifier 205, and flocculanttank 220 is optional.

Similar to FIG. 1, effluent 230 may enter coagulation tank 210, whichmay provide coagulated effluent stream 250. Stream 250 may enter ballastmixing tank 215, which may provide ballasted effluent stream 255. Stream255 may enter flocculation tank 220, which may provide flocculatedeffluent stream 260. Stream 260 may then enter the clarification portionof clarifier 205. Treated effluent stream 265 may exit clarifier 205.Meanwhile, a separate ballasted solids stream 270 may exit clarifier 205at a different outlet from that of treated effluent stream 265. Aportion of the ballasted solids may be diverted to a returned ballastedsolids stream 275 that may feed ballast feed tank 215. At least aportion of the ballasted solids stream 270 may be directed to ballastrecovery system 280. The ballast recovery system 280 may produce arecovered ballast stream 290 which may be directed to ballast feed tank215. The ballast recovery system 280 may produce a ballast-free solidsstream 285, or solids waste stream, directed for further processing orreturned to a part of the waste treatment system.

In certain embodiments of the present disclosure, a method ofretrofitting a wastewater treatment system may be provided. Thewastewater treatment system may comprise a fixed film bioreactor and aclarifier positioned downstream of the fixed film bioreactor. Theclarifier may comprise a solids outlet. The method may compriseinstalling a coagulation tank in the clarifier. The method may furthercomprise installing a ballast feed tank connected downstream of thecoagulant tank in the clarifier. The method may further compriseconnecting the solids outlet of the clarifier to the ballast feed tank.The method may further comprise installing a ballast recovery systemdownstream of the solids outlet of the clarifier and upstream of theballast feed tank. The method may further comprise installing aflocculation tank in the secondary clarifier connected downstream of theballast feed tank.

The function and advantage of these and other embodiments of the systemsand techniques disclosed herein will be more fully understood from theexample below. The following example is intended to illustrate thebenefits of the disclosed treatment approach, but do not exemplify thefull scope thereof.

EXAMPLES Example 1

A wastewater stream from a source of wastewater was delivered to threefixed film moving bed bioreactor (MBBR) tanks in series after passingthrough coarse screening, grit removal, and a fine screen. The screenedwater was pumped to the MBBR tanks at an average flow rate of 2.1gallons per minute (GPM). The flow then passed through a 6 foot diameterby 7 foot deep secondary clarifier. Samples were taken from the effluentprior to being passed through the secondary clarifier. The samples wereplaced into liter beakers with coagulant dosages of 10 to 60 ppmv, withferric chloride as the coagulant. Magnetite at 10 g/L was added to eachbeaker. The samples were mixed for three to six minutes, and thenallowed to settle. All samples settled rapidly in 15 to 30 seconds, withsettling results ranged from 0.2 to 2.9 mg/L effluent total suspendedsolids. All effluent in the beakers appeared clear at each does ofcoagulant.

These results may be compared to a fixed film MBBR system that isfollowed by a secondary clarifier in which about 90 ppmv of ferricchloride is used, which results in an effluent of the clarifier having25 to 35 mg/L total suspended solids.

These results show that using a fixed film MBBR process in conjunctionwith a magnetic ballast system enhanced the quality of the treatedwater, reducing the total suspended solids. This process also requiredless coagulant to be used in the process. This system provides enhancedtreatment of the water as well as provide cost savings in terms of usingless coagulant than a conventional system.

Example 2

Wastewater was processed through a treatment system comprising atrickling filter and a secondary clarifier. The flow rate of wastewaterentering the trickling filter was about 600 GPM to about 700 GPM. Acoagulant (alum) was added to the effluent of the trickling filter atconcentrations ranging from about 100 ppmv to about 300 ppmv. Fifty GPMof effluent from the trickling filter was diverted to a processcomprising a ballasted flocculation system in which magnetite was addedto the trickling filter effluent.

Data regarding biological oxygen demand (BOD) was measured for a systemincluding a trickling filter whose effluent was either treated in aballasted flocculation system or a secondary clarifier. Samples weretaken over a two week period. This data is shown in Table 1.

TABLE 1 BOD in Effluent after BOD in BOD in BOD in Trickling FilterEffluent after Effluent from Feed to into Ballasted Ballasted SecondaryTrickling Flocculation Flocculation Clarifier Sample Filter (mg/l)(mg/l) (mg/l) (mg/l) 1 75 51 3 Not tested 2 87 46 4 22 3 81 28.1 9.55 124 Not tested 20.6 3.9 10 5   91.4 29.6 2.6  4

As shown above in Table 1, the BOD of the effluent after treatment withthe ballasted flocculation system was improved over effluent that wastreated with a secondary clarifier. These results demonstrate theimproved treated water product that may be obtained by using theballasted flocculation process over a conventional secondary clarifier.

Data was also collected from testing using the ballasted flocculationsystem and is shown in Tables 2-5.

TABLE 2 Total Suspended Total Suspended Total Solids in Effluent Solidsin Suspended of Trickling Filter, Effluent after Solids in Feed goinginto Ballasted Ballasted to Trickling Flocculation Flocculation SampleFilter (mg/l) (mg/l) (mg/l) 1 117 110  3 2 127  89 73* 3 110  95  3 4 40  43  4 5  45  34  2 *In this run, no alum was added.

As shown above in Table 2, total suspended solids was decreasedsubstantially through use of the ballasted flocculation process.

TABLE 3 Total Phosphorus from Total Phosphorus Trickling FilterEffluent, in Ballasted going into Ballasted Flocculation ClarifierSample Flocculation (mg/l) Effluent (mg/l) 1 5.46 0.061 2 5.34 0.131 34.66 0.047 4 3.97 2.36 5 4.01 0.314

As shown in Table 3, phosphorus levels were reduced through use of theballasted flocculation process.

TABLE 4 Turbidity in Trickling Turbidity in Filter Effluent, goingEffluent after into Ballasted Ballasted Sample Flocculation (NTU)Flocculation (NTU) 1 95  3.1 2 65  8.9 3 40 12.5 4 40  4.1 5 50 Nottested

As shown in Table 4, turbidity was reduced through use of the ballastedflocculation system.

While exemplary embodiments of the disclosure have been disclosed, manymodifications, additions, and deletions may be made therein withoutdeparting from the spirit and scope of the disclosure and itsequivalents, as set forth in the following claims.

Those skilled in the art would readily appreciate that the variousconfigurations described herein are meant to be exemplary and thatactual configurations will depend upon the specific application forwhich the system and methods of the present disclosure are used. Thoseskilled in the art will recognize, or be able to ascertain using no morethan routine experimentation, many equivalents to the specificembodiments described herein. For example, those skilled in the art mayrecognize that the system, and components thereof, according to thepresent disclosure may further comprise a network of systems or be acomponent of a wastewater treatment system. It is, therefore, to beunderstood that the foregoing embodiments are presented by way ofexample only and that, within the scope of the appended claims andequivalents thereto, the disclosed system and methods may be practicedotherwise than as specifically described. The present system and methodsare directed to each individual feature or method described herein. Inaddition, any combination of two or more such features, apparatus ormethods, if such features, system or methods are not mutuallyinconsistent, is included within the scope of the present disclosure.

Further, it is to be appreciated various alterations, modifications, andimprovements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe disclosure. For example, an existing facility may be modified toutilize or incorporate any one or more aspects of the disclosure. Thus,in some cases, the apparatus and methods may involve connecting orconfiguring an existing facility to comprise at least one of a fixedfilm system, a clarifier, and a ballasted flocculation system.Accordingly, the foregoing description and drawings are by way ofexample only. Further, the depictions in the drawings do not limit thedisclosures to the particularly illustrated representations.

As used herein, the term “plurality” refers to two or more items orcomponents. The terms “comprising,” “including,” “carrying,” “having,”“containing,” and “involving,” whether in the written description or theclaims and the like, are open-ended terms, i.e., to mean “including butnot limited to.” Thus, the use of such terms is meant to encompass theitems listed thereafter, and equivalents thereof, as well as additionalitems. Only the transitional phrases “consisting of” and “consistingessentially of,” are closed or semi-closed transitional phrases,respectively, with respect to the claims. Use of ordinal terms such as“first,” “second,” “third,” and the like in the claims to modify a claimelement does not by itself connote any priority, precedence, or order ofone claim element over another or the temporal order in which acts of amethod are performed, but are used merely as labels to distinguish oneclaim element having a certain name from another element having a samename (but for use of the ordinal term) to distinguish the claimelements.

1. A system for treating wastewater comprising: a fixed film reactorfluidly connected to a source of wastewater and configured to provide afixed film effluent; a source of ballast fluidly connected to the fixedfilm effluent and configured to provide a ballasted effluent; and aclarifier fluidly connected to the ballasted effluent, the clarifiercomprising a treated effluent outlet and a ballasted solids outlet andconfigured to separate a treated effluent from a ballasted solids. 2.The system of claim 1, further comprising a source of flocculant fluidlyconnected to the ballasted effluent.
 3. The system of claim 1, furthercomprising a source of coagulant fluidly connected to the fixed filmeffluent and configured to provide a coagulated effluent.
 4. The systemof claim 1, wherein the fixed film reactor comprises at least one of amoving bed bioreactor, a trickling filter, and a rotating biologicalcontactor.
 5. The system of claim 1, wherein the fixed film effluentcomprises about 50 mg/l to about 300 mg/l of biological solids.
 6. Thesystem of claim 1, wherein the ballast comprises magnetite.
 7. Thesystem of claim 1, wherein the system is configured to treat betweenabout 200 gallons per day per square foot of a surface area of theclarifier to about 6,000 gallons per day per square foot of the surfacearea of the clarifier.
 8. The system of claim 3, wherein the ballastedsolids outlet of the clarifier is fluidly connected to at least one ofthe coagulated effluent and the fixed film reactor.
 9. The system ofclaim 8, further comprising a ballast recovery system positioneddownstream of the ballasted solids outlet of the clarifier and upstreamof at least one of the source of ballast and the fixed film reactor.10.-20. (canceled)